Centrifugal compressor



Jan. 1, 1946. w. s. THOMPSON CENTRIFUGAL COMPRESSOR Filed Nov. 27, 1944lfivefitorz VencleLL S.Thomps01"n,- by '4 I Hi Attorney.

. halves i, 2.

Patented Jan. 1, 1946 UNITED STATES PATENT OFFICE CENTRIFUGAL COMPRESSORNew York Application November 27, 1944, Serial No. 565,201

Claims.

The present invention relates to centrifugal compressors with variablediffusers for operation within a wide range of load or capacity as isrequired in connection with the supercharging of aircraft engines andcabins.

The Object of my invention is to provide animproved construction ofcentrifugal superchargers,

more particularly of the diffusers thereof whereby they may be operatedwithin a'wide range at high efficiency.

For a consideration of what I believe to be novel and my invention,attention is directed to the following description and theclaims'appended v halves l and 2 flanged together and forming animpeller chamber 3 with aninlet 4 formed by the casing half l and adischarge scroll 5. An impeller 6 is disposed within the impellerchamber 3 and secured to a shaft rotatably supported on a bearing 3.During operation, medium such as air to be compressed passes through theinlet :3 and is forced radially outward by the impeller 6 into thescroll 5,'whence it is discharged through a flanged outlet conduit 9formed by the casing Diffuser means are provided to convert part of thevelocity energyof the compressed medium discharged from the impellerinto pressure sperm. This diffuser means surrounds concentrically theimpeller B and in the present example is located substantially in thedischarge scroll 5. More specifically, the diffuser comprises twoaxially spaced side walls or rings 'IB and II. The wall Ill is seated onshoulders formed by the casing half 5 and secured thereto bycircumferentially spaced screws It. The wall or ring H is seated on ashoulder formed by the casing hall 2 and secured thereto bycircumferentially spaced bolts or screws l3. A set of circumferentiallyspaced, curved difiuser vanes M is located between the side walls orrings Ill and H. In the present example the set of vanes 14 isintegrally formed with the wall i l. Adjacent vanes It form diffuserpassages between them, which passages increase gradually incross-sectional area from the radiallyv inner ends ,or inlets toward theradially outer ends or outlets.

The difiuser so far described is typical of diffuser arrangements usedin present day centrifuinto a comparatively gal compressors; Thesediffusers operate well within a small load range only. through thecompressor drops below a certain value this type of diffuser causespulsations and renders the compressor unstable. In order to reduce suchpulsations and to permit a wider load range I provide in accordance withmy invention additional difiuser vanes adjustably arranged be tween theaforementioned set of stationary vanes. In the present instance theembodiment in the drawing includes a second set of difiuser vanes,wedges or control members It. Each of these vanes is centrallylocatedbetween a pair of vanes Hi and subdivides the passage formedtherebetween. More specifically, each vane is in the form of awedge-shaped member having a comparatively thin inner portion-taperinggradually thick outer portion.

Each Wedge or wedge-shaped member 55 forms a tongue and grooveconnection with the walls it, ii. To this end each wedge 65 is providedon opposite edges with tongues it slidably projecting into curvedopenings ll and grooves it formed in the side walls Hi, i i,respectively. Each wedge forms with adjacent, stationary vanes iii apair of diffuser passages i9, 20, Fig. 2. The width of the dififuserpassages i9, 28, more particularly the throat area thereof, is a minimumwhen the wedges or adjustable vanes 55 are moved into their inner endposition, and the throat area be come maximum as the wedges iii aremoved into their radially outer end positions. The end positions aredetermined by engagement between the ends of the tongues it with thecorresponding ends of the openings ii and grooves it.

The arrangement according to my invention includes means for adjustingor positioning the adjustable diffuser vanes or wedges along the centerliens or how lines between the stationary vanes M. This adjusting orpositioning means comprises a ring 2! with a plurality ofcircumierentially spaced radial openings or slots 22 each for receivinga pin 23 projecting axially- Iroma tongue 58 of each wedge If). The ring2! has a toothed portion with a pinion 25. The latter is secured to ashaft 25 rotatably supported on the casing half l. During operation,rotation of the shaft 28 causes turning movement of the pinion 25' whichin turn effects angular displacement or movement of the ring 2!. Thelatter through its slot and pin connections with the wedges oradjustable vanes i5 causes the latter to move along their center lines,that is, along the grooves 11, I8. Upon rotation of the pinion 25 in onedirection or rack 24 meshin 2 asoaaoo the wedges II are moved inward toreduce the minimum flow area or throat or the adjacent difluser passagesand upon rotation of the pinion 2! in the opposite direction the wedgesare moved outward to increasethe throat area of the adjacent difluserpassages. The curved wedge shape of the adjustable vanes or wedges andthe positioning thereof along the center lines between adjacentstationary vanes it smooth diffuser passages and accordingly efiectiveandefllcient diil'us'ion within a wide range of load. Thus, with myinvention I have accomplished an improved difluser arrangement whichbroadly comprises a pair of axially spaced walls I or rings with a setof circumferentially spaced stationary vanes between them and anotherset tionary vanes.

3. Difluser arrangement for centrifugal compressors comprising a ringwith a plurality of circumferentially spaced stationary vanes, a

1 plurality of adjustable vanes located between the assures ofwedge-shaped vanes alternating with the impeller disposed in theimpeller chamber, and

a variable diffuser for conducting compressed medium discharged from theimpeller into the scroll, said difiuser comprising axially spaced sidewalls supported on the casing, a set of circumferentially spacedstationary vanes held on the side walls and a set of circumferentiallyspaced adjustable wedge-shaped vanes each centrally located between apair of stationary vanes, and means for moving the adjustable vanesalongv the center lines'.between the stationary vanes.

2. Difluser arrangement for centrifugal compressors comprising a pair oiaxially spaced rings, a set of circumferentially spaced curvedstationary vanes located between the rings and secured to one of them,and a set of adjustable vanes located between the stationary vanes anddividing the passages between the stationary stationary vanes andforming tongue and groove connections with the ring, and means formoving the adjustable vanes along the center lines I between adjacentstationary vanes to vary the flow area of the passages formedbetween thevanes; a

4. Difluser arrangement for centrifugal compressors comprising a pair ofaxially spaced rin s. a set of stationary circumferentially spacedcurved vanes secured to the rings and forming diffuser passagestherewith and a set of adjustable circumierentially spaced curvedwedge-shaped vanes interspersed between the stationary vanes andsubdividing the diifus'er passages formed thereby, each stationary vanehaving curved tongues on opposite edge portions located in grooves inthe rings between stationary vanes, and means for moving the ad-'justable vanes along the grooves to vary the diffuser passagesformedbetween them and the stationary vanes, said means comprising axiallyextending pins secured to the. tongues, a ring having circumierentiallyspaced substantially radial slots for receiving the respective pins andgear means for angularly positioning said last named ring.

5. Difluser arrangement for centrifugal compressors comprising a pair ofaxially spaced annular'walls, a pair of stationary circumferentiallyspaced vanes supported between said walls and cooperating therewith toform a diilusing passage, a tapered control member located within thediffusing passage, and means for adjustin the member substantially alongthe center line of the passage to vary the eflective area thereof.

Y WENDELL S. THOMPSON.

vanes, and means for positioning the adjustable vanes along the centerlines between the sta-

